1. Field of the Invention
The present invention relates to a method and an apparatus for creating a frame of an orthogonal frequency division multiplexing (OFDM) specification, and more particularly, to a method and an apparatus for creating a frame of an OFDM specification using frequency domain spreading.
2. Description of the Related Art
Physical layer (PHY) specifications for the Smart Utility Network to facilitate metering electricity, gas, and water wirelessly are standardized based on the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4g.
An orthogonal frequency division multiplexing (OFDM) transmission scheme performing the standardization on the IEEE 802.15.4g provides an interleaving structure to maximize effects of frequency domain spreading (FDS) and channel coding for a high link margin. Since there is a close relation between a size of the interleaving structure and the FDS in forming a frame, it is difficult to form the frame when the relation between the size of the interleaving structure and the FDS is not clearly defined.
Embodiments of the present invention disclose frame forming methods generally applied to various options depending on a size of a fast Fourier transform (FFT) of the OFDM defined in the IEEE 802.15.4g specification.
Installation of a smart grid, an intelligent electricity network, actively encouraged to as a strategic project by countries in the world, is intended to reduce costs through efficient energy management and to reduce carbon emission produce through production of renewable energy. Advanced countries, such as the USA and European countries, have implemented various IT-based electric power network projects since early 2000, and the Korean government also launched a national project and program in 2009.
The IEEE 802.15.4g Task Group receives a suggestion and standardizes the SUN PHY specifications, a wireless electricity metering system, used in a wireless network of the smart grid since May in 2009. The suggested technology will be developed into a wireless system specializing in the wireless network of the smart grid to provide a high link margin so that a low-power design is realized and inadequate surroundings for radio signals are overcome.
The embodiments of the present invention suggest frame forming methods based on FDS and a size of an interleaving structure designed to provide a high link margin so that a low-power design is realized and inadequate surroundings for radio signals are overcome, which are required by the IEEE 802.15.4g SUN specification group. The methods are distinguished from conventional system forming methods proposed for OFDM system specifications developed ignoring FDS characteristics.